The present invention relates to an apparatus for monitoring irregularities in a textile yarn being produced by an open-end spinning turbine, the apparatus being of the type which employs a measuring value sensor to detect the irregularities and an evaluation circuit which, upon the occurrence of irregularities, in particular a predetermined number of irregularities, per given time interval or during irregular time intervals, emits a signal to a display and/or to switch off the spinning turbine.
Such an apparatus is disclosed in German Offenlegungsschrift [Laid-Open Application] No. 2,509,259. That apparatus includes a measuring value sensor disposed in the yarn removal path to generate an analog signal which is representative of the thickness of the yarn. A pulse is generated each time this analog signal exceeds a threshold value, i.e. when the thickness of the yarn exceeds a selected value, and the resulting pulses are counted in a counter, the occurence of at least a given number of pulses within a given period of time causing a display or switch-off signal to be emitted.
Monitoring of the yarn being produced in an open-end spinning machine is recommended because irregularities, particularly thickness variations in the yarn may occur irregularly in cycles or even at regular intervals and thus would lead to undesirable moire effect in fabrics produced from that yarn.
Such thicker or thinner portions are produced mainly as a result of deposits of dirt particles in the rotor of the spinning turbine.